Possible nuclear power station impacts on near-shore marine habitats - - PowerPoint PPT Presentation

Slide 1

Possible nuclear power station impacts

• n near-shore marine habitats

(with special reference to Thyspunt)

Prof Charles Griffiths and Dr Tammy Robinson

Marine Biology Research Centre University of Cape Town Charles.Griffiths@uct.ac.za

Slide 2

Background:

Thyspunt lies in the centre of the large, relatively uniform Warm-temperate ‘Agulhas Bioregion’ of South Africa

Slide 3 Source: SA State of the Environment Report 2004 B iozo ne P ro tection S tatus

W ell p ro tecte d M

• d

era te ly pro te cted P

• rly p

ro te cte d H ardly protected Z e ro p ro te ction

In te rtidal D e ep pho tic S h allow pho tic S ub ph

• tic

S up ratidal

This bioregion is considered to be ‘well protected’ (in terms of protected areas) and is the least threatened coastal biozone in the region (in terms of exploitation pressure, mining etc)

B iozone Threat S tatus

C ritica lly endan gered E ndangered V uln erable Least thre atened

Intertidal D eep pho tic S hallow p hotic S u b ph

• tic

S upratid al

Slide 4

All groups combine

200 400 600 800 1000 1200 1400 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Distance around the coast (100 km un

Removed endemic Endemics 20 40 60 80 100 120 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Distance around coast (100 km un

Species per 100 km stretch 1= Orange R 8= Cape Town 15 = Thyspunt 16= Port Elizabeth 24= Durban Range-restricted species Per 100 km stretch (range <300km)

It lies in an area of high overall species richness and endemicity (bar 15), but contains very few unique or range-restricted species (lower fig.)

Slide 5

Potential nuclear power-station impacts on marine environment:

• 1. Entrainment and death of fish and plankton in intake water
• 2. Death of local fauna as a result of construction work, spoil dumping, etc
• 3. Release of heated water and/or brine from desalination plants
• 4. Changes in current patterns due to breakwaters, etc
• 5. Creation of habitat (e.g. hard substrata where only beach existed before)
• 6. Access control, leading to less angling and disturbance (conservation areas)

Note: Release of radio-isotopes into the sea is not considered a threat, as cooling water never comes into contact with the reactor.

Slide 6

Entrainment of marine organisms in cooling water:

• Pumping, plus chlorination, of cooling water at Koeberg

results in mortality of 28% phytoplankton and 43-68% of zooplankton in pumped water

• Almost no larger fish or other marine species are entrained

and killed

• Wider impacts undetectable, given the much larger natural

water flow through the area and the short doubling time of plankton in the cooling water

Slide 7

Construction and dumping: (Regarded as the main environmental impact of concern)

• Tunneling to lay water intake pipes and laying of outfall

pipes will disrupt limited areas of seabed

• Dumping of spoil can be expected to smother bottom-

dwelling species over area approx 3 km2 and may affect chokka squid spawning areas, but only by a few %

• This effect will be focused within the construction phase

and will be localised and of limited duration (a few years)

• Recovery (spoil dispersion and colonisation) can be

anticipated to take place over several years

Slide 8

Release of heated water:

• Volume minimal in comparison with natural flows (ca 80 m3.sec at Koeberg vs

60 million m3.sec for Agulhas Current)

• No temperature elevation >2oC detected more than 1 km from outfall at

Koeberg

• Warmed plume water floats, so does not effect bottom–dwelling species
• Twice yearly surveys at Koeberg have revealed no detectable changes in biota,

even within 1 km radius

• Any warming at Thyspunt is taking place in context of a long term cooling

trend in region, as depicted below.

Sea temp changes 1985-2007

Slide 9

Release of desalination brine:

• More problematic than heating, as heavier than seawater, so sinks
• Could result in impacts during construction phase, but over limited area

and limited duration of this phase

• During operational phase will be mixed with heated water, resulting in

high dilution and reduced density, impact expected to be undetectable Changes in current pattern and habitat type:

• Impacts trivial at this site, as hard substrates and complex shore

topography already present and no stilling basin to be constructed

• Any additional hard substratum simply provides more habitat for attached

species Controlled access:

• Results in enhanced fish stocks and diffusion of protected fish into adjacent

angling areas, but as this particular site is already restricted, little additional benefit is to be gained

Slide 10

Overall marine impacts - conclusions:

• Limited negative impacts expected during construction phase,

mainly due to release of saline water and construction activities (excavation, dumping of spoil, etc).

• Area of impact a few km2 ( South Africa’s EEZ = 1 million

km2)

• Recovery expected to be measured in years (not decades)
• Marine impacts during operational phase expected to be

undetectable, as is currently the case for Koeberg

• Positive impacts expected from conservation of site expected to

continue

End